1. Field of the Invention
This invention relates to an automatic soldering apparatus.
2. Description of the Prior Art
In order to form a solder film on each lead of an integrated circuit device (hereinafter called a "work" or "IC"), typical prior art technique such as one disclosed in Japanese Patent Publication No. 57269/1983 employs the steps of fitting a large number of works to a fixture, supplying this fixture to an automatic soldering apparatus and soldering automatically the leads.
In the conventional automatic soldering apparatus of the prior art reference described above, an endless conveyor for conveying the fixture is provided, and various unit of equipment such as a pre-treating tank for removing contamination of the works, a fluxer for putting a flux to the works, a pre-heater for pre-heating the works, a solder tank for jetting a molten solder to the leads, a washing tank for removing the remaining flux, a drying heater for drying the washing liquid, and so forth, are arranged sequentially along the endless conveyor.
Among the various equipment used for soldering described above, some must be replaced from time to time by others or be entirely removed depending upon types of works to be soldered.
When many equipment units are disposed along the endless conveyor for soldering as described above, however, it is not possible to replace or remove some of them.
Next, the conventional fixture will be explained. As described in Japanese Patent Publication No. 57269/1983 described above, a soldering fixture for aligning and supporting a large number of integrated circuit devices (hereinafter called "works") has been used in the past in order to solder their leads.
In the known fixture of the type described above, a lower support line member and an upper support line member are disposed inside the same frame and a large number of works are continuously slid and inserted between both support line members from an insertion port defined on the frame, and after a gate member formed at the insertion port is closed, the fixture is fitted to a conveyor holder of the soldering line.
The known fixture described above is suitable for the works of the type which have leads on two faces of an IC package such as dual in-line package type IC, and the leads on both sides of the work are put and slid on the lower support line member in such a manner as to bridge the lower support line member.
However, a flat package type IC which has gained an increasing application recently as a surface mount type IC for a printed circuit board and in which leads are disposed on four faces of the IC package cannot be fitted to the known fixture described above because the leads disposed in the longitudinal direction interfere with the lower support line member at the time of insertion.
Japanese Patent Application No. 289019/1985 (hereinafter called the "application A") therefore discloses a fixture for soldering the leads of the four-face lead type IC. As disclosed in the specification and drawings of this prior art reference, at least one pair of lower support members are disposed in parallel with each other with a gap between them inside an outer frame, a recess is formed on the upper surface of each lower support member in a direction orthogonal to the gap, fitting grooves into which four corners of the IC package are to be fitted are defined at the four crossing points between the gap and the recesses, an inner frame is removably inserted from above into the outer frame, and upper anchor members for anchoring the upper surface of the IC package fitted to the lower support members are disposed inside the inner frame along the lower support members. Another fixture is disclosed in Japanese Patent Application No. 145670/1986 (hereinafter called the "application B"). As disclosed in the specification and drawings of this prior art reference, this fixture has a construction wherein receiving members are disposed inside an outer frame, projections for supporting the lower surface of the IC package are integrally molded with the upper side of the receiving members, support members are removably fitted from above into the outer frame, and recesses that fit to the upper part of the IC package placed on the projections are formed on the support members.
In the fixture of the application A, the inner frame is fitted into the outer frame into which the works have been already fitted, by gripping a handle disposed in the inner frame, while in the fixture of the application B, the support member is fitted into the outer frame by gripping a handle disposed on the support member. In either case, the work fixing member disposed at the upper part of the work is gripped by hand and inserted into the outer frame, but this fitting work is based on the premise that accurate locating of the work is made between the outer frame and the work fixing member, and this is a problem to be solved in order to accomplish automatic soldering.
Thirdly, an automatic work feeding and discharging apparatus for automatically feeding and discharging the works to and from the fixture conveyed endlessly in the automatic soldering apparatus will be explained. As described in Japanese Patent Publication No. 57269/1983 mentioned already, a conventional method comprises transferring the works from a work case (work storage tube) to the fixture by use of a seesaw type work transfer device outside the automatic soldering apparatus, removing then the fixture from the work transfer device, fitting the fixture from above to a conveyor holder constituting the conveyor line of the automatic soldering apparatus and soldering the leads of the works while conveying the fixture together with the conveyor holder.
Moreover, since the work transfer device described above transfers the works from the work case to the fixture by a slide system, its application is limited to integrated circuit devices (ICs) of a dual in-line type but not to a surface mount type IC such as a flat package type IC in which leads extend from the entire periphery of the IC package, for example.
As described above, it has been customary to individually supply the fixture having the works fitted thereto to the conveyor line of the automatic soldering apparatus through a manual operation by the workers. Therefore, the conventional system is not free from the problems in that the load to workers is great and the system cannot be changed to accept the surface mount type ICs.